<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script src="js/vue.js"></script>
    <div id="app">
        <div v-bind:style="{color:activeColor,fontSize:fontSize+'px'}">Hello World!</div>
        <div v-bind:style="styleObj">Vue.js</div>
    </div>

    <script>
        var vm = new Vue({
            el: "#app",
            data: {
                activeColor:'red',
                fontSize:30,
                styleObj:{
                    fontSize:'30px',
                    'text-decoration':'underline'
                }
            }
        })
    </script>

</body>

</html>